During the early stages of construction, it is often necessary to cast concrete footers for foundations. The first step is to dig an earthen trench or ditch into which the concrete footer will be cast. The height of the concrete casting is then determined by the use of the surveyor's scope or the more modern laser method. In any event, that position must then be marked so that the workers will cast the concrete to the correct height. Marking is effected by the use of physical markers placed at short intervals, normally three to five feet, along the length of the entire ditch.
Insofar as is known, all currently used markers for marking the grade of the concrete to be cast are relatively costly and require substantial physical work and manhours to use. By far the most commonly used technique is for the workman to merely drive a wooden stake or iron rod, normally pounded with a sledge hammer, vertically into the center of the ditch. This is done to a selected depth in conjunction with the surveyor so that the top of the stake ill be at precisely the upper level of the footer or foundation to be cast. The concrete is then poured to the top of the stake or rod and the proper level is obtained.
A lesser known method is sometimes known as the nail and ribbon technique. The workers carry with them sixteen penny nails and plastic ribbon. Each nail is stuck through a short length of plastic ribbon folded into a square. The nail is then inserted horizontally into the side of the ditch at the level instructed by the surveyor. The cement is then poured to the center of the nail head, the ribbon being used to make the nail head more visible against the dirt. One reason this technique is not as widely used as the aforementioned vertical stake method is that the nail does not as accurately show the upper level to which the concrete is to be cast, i.e. the nail head having a rather large diameter does not give an accurate horizontal level, and especially from the seat of the concrete casting device it is not readily apparent from the ribbon on the nail exactly where the upper level of the concrete should be. Other disadvantages of this system are that sixteen penny nails are quite heavy and the workman do not like to carry a large quantity of them; the plastic ribbons have to be cut which causes delays; and the large sixteen penny nails are relatively expensive.
The problems outlined above, which incidentally exist in other construction environments as well such as the laying of sewer lines, the construction of leech beds for the installation of septic tanks, etc., have so far not been solved and present an ongoing problem in various construction environments.